Synchiropus splendidus, the mandarin fish or otherwise identified as the mandarin dragonet, is a small, brightly coloured member of the dragonet family, popular within the saltwater aquarium trade. The mandarin fish is native to the Pacific, ranging approximately from the Ryukyu Islands southward to Australia. It can usually be found in a number of the more temperate waters & ocean waters.
The mandarin fish was first described as Callionymus splendidus in 1927 by Albert William Herre, an American ichthyologist working within the Philippines. It had been later placed in the genus Synchiropus. The generic name Synchiropus is from the Ancient Greek syn -, meaning “together”, and -chiropus meaning “hand-foot”.
The precise epithet splendidus is from the Latin for ‘bright’ or ‘glittering.’ The common name of the mandarin fish comes from its extremely vivid colouration, evoking the robes of an Imperial Chinese mandarin.
Other popular terms include mandarin goby, green mandarin, striped mandarin fish, striped dragonet, a green dragonet, and sometimes psychedelic mandarin fish. The similarly named mandarin fish (Siniperca chuatsi), properly referred to as the Chinese perch, is distantly related.
The mandarin fish belongs to Callionymidae’s perciform family, the dragonets, which counts ten genera and over 182 species. Genus Synchiropus counts 51 species, divided into ten subgenera. The mandarin fish is in subgenus Synchiropus (Pterosynchiropus) alongside the S. occidentalis and S. picturatus.
Mandarin Fish Description
S. splendidus or the Mandarin Fish is one of only two vertebrate species known to possess blue colouring due to cellular pigment, the other being the closely related psychedelic mandarin (S. picturatus). The name “cyanophore” was proposed for the blue chromatophores, or pigment-containing & light-reflecting cells.
The colour blue is structural because it comes from thin-film interference from piles of the flat, thin, and reflecting purine crystals. The mandarin fish features a body shape just like a goby, though this is the sole resemblance between the two. The vivid coloration sports an azure or bright blue background, with swirly orange stripes and a blue-greenish face with bold blue lines.
The massive pelvic fins are used for ‘walking’ on the seafloor and are often mistakenly seen because of the pectoral fins. The primary pectorals are located almost at the middle and are nearly transparent, with a tinge of a fin, the anal fins, and on the part of the tail, the remainder of which is striped in vibrant orange & blue. The dorsal fin, which is particularly tall in the males, features a striking orange-and-blue design also.
The eyes are usually red with black pupils – different sports, markings, and colours. The green mandarin fish is the fish that has been described. The red mandarin fish is the same species, but its pelvic fins and orange are red. In some rare cases, the whole dragonet is red with black stripes. The spotted mandarin fish is light gray-green with blue, black & pink spots.
Mandarin fish are reef dwellers, preferring sheltered lagoons & inshore reefs. While they’re slow-moving and relatively common within their range or species, they’re not easily seen thanks to their bottom-feeding habit and small size (reaching only about 6 cm). They feed mostly on the smaller crustaceans and other invertebrates.
Mandarin Fish Diet
Based on the gut analyses of seven wild fish, Sadovy et al. (2001) determined that the mandarin fish features a mixed diet that consists of harpacticoid copepods, polychaete worms, small gastropods, gammaridean amphipods, fish eggs, and ostracods.
Within the wild, feeding is continuous during daytime; the fish peck selectively at small prey trapped on the coral substrate in a home territory of many square meters.
Relevance to humans
Despite their reputation within the aquarium trade, mandarin fish are considered difficult to look after, as their feeding habits are particular. Some fish never adapt to aquarium life and refuse to eat anything but live amphipods and copepods (as within the wild), though individuals who acclimatise to aquarium food are considered to be quite hardy and highly immune to diseases like marine ich.
They’re less likely to contract marine ich because they don’t have the standard skin type suffering from this disease. The Mandarin fish even has a debatably smelly and bitter slime layer rather than scales, which blocks out disease and possibly discourages predators, implying their bright coloration is aposematic.
The mandarin fish appeared on a 39-kip stamp from Laos issued in 1987, and a 40-cent stamp of the Federated States of Micronesia issued on 26 August 1993.
Beware of the gorgeous but poisonous Mandarinfish
The mandarin Fish is the most beautiful fish within the sea, but the mandarin fish (Synchiropus splendidus) has got so much more happening for it than all those pretty colours.
At home within the sheltered lagoons and inshore reefs of the Pacific, starting from the Ryukyu Islands the shoreline of Japan, to warm Australian waters, this tiny dragonet is covered by small spines to inject a toxic mucus into anyone who tries to handle and eat it.
The mandarin fish contains two kinds of secretary cells in its colourful epidermis – one that produces a thick mucus coating to guard it against the elements and another that has a toxin to protect it from predators. And not only is that this toxic mucus coating dangerous, essentially if it makes it into a predator’s open injury, reportedly, but it also smells disgusting.
“Every scientist and book [who] talks about the mandarin fish makes mention of its strong, unpleasant smell,” says Esther Inglis-Arkell at io9. “That stink isn’t incidental. The mandarin fish needs the smell, and therefore the spines, because it lacks one of the most basic protective measures within the marine world: It doesn’t have scales.”
There’s nothing like thick slime & an unpleasant odor to turn someone off their potential meal.
Mandarinfish produces a blue pigment.
And credit where credit’s due because it’s challenging looking this good and smelling that bad: the mandarin fish is one amongst just two confirmed species within the world which will produce its blue colouring. With its near relation, the psychedelic mandarin (Synchiropus picturatus), the mandarin fish creates ‘cyanophores’ – blue pigmented, light-reflecting cells – to attain its lively colouring.
As I discussed previously, the overwhelming majority of blue-hued creatures on the planet need to create optical illusions to decorate themselves up, with microscopic layers of colourless crystals in their skin in such a way that they give off this brilliant blue colour to any onlooker.
MandarinFish Care Guide:
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